TWI642916B - Overheat detection circuit and semiconductor device - Google Patents

Abstract

An overheat detection circuit that can accurately detect the temperature of a semiconductor device even at a high temperature and does not output an erroneous detection result.

As a first PN junction element as a temperature sensing element, a constant current circuit that supplies a bias current to the first PN junction element, a comparator that compares a voltage generated by the first PN junction element with a reference voltage, and a reference to a high temperature The second PN junction element in which the voltage circuit flows a leakage current and the third PN junction element in which the leakage current of the constant current circuit is bypassed at a high temperature.

Description

Overheat detection circuit and semiconductor device

The present invention relates to an overheat detecting circuit that can detect an abnormal temperature of a semiconductor device.

Previous overheat detection circuits are known to have circuits as shown in the prior art documents.

Figure 3 is a circuit diagram of a prior overheat detection circuit. The conventional overheat detecting circuit includes a reference voltage unit 10, a temperature sensing unit 20, and a comparator 30. In the conventional overheat detecting circuit, the voltage generated by the PN junction element 21 which is the temperature sensing element is compared by the comparator 30, and the reference voltage Vref output from the reference voltage circuit 11 detects the overheated state. The voltage generated by the PN junction element 21 is substantially a negative temperature characteristic as long as the PN junction element 21 is biased by the constant current of the constant current circuit 22. When the ambient temperature becomes high and the voltage generated by the PN junction element 21 is lower than the reference voltage Vref, the comparator 30 outputs a signal indicating the overheated state.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 6-242176

However, the above-described overheat detecting circuit is, for example, a state in which the constant current circuit 22 is constituted by a current mirror circuit of a PMOS transistor, and the like, because the leakage current between the drain terminal of the PMOS transistor and the substrate increases when the temperature is high. The constant current biased by the PN junction element 21 also increases. Therefore, since the voltage of the PN junction element 21 rises, there is a problem that the temperature cannot be detected correctly.

Further, for example, the NMOS transistor in which the reference voltage circuit 11 is saturated is provided, and the leakage current between the NMOS terminal of the NMOS transistor and the substrate increases at a high temperature, and the reference voltage Vref of the reference voltage circuit 11 increases. Since it is reduced, there is a problem that the temperature of the comparator 30 cannot be detected correctly.

Further, for example, the leakage current of the transistor constituting the comparator 30 increases, and an abnormality occurs in the internal operation, and there is a problem that the temperature cannot be accurately detected and the result cannot be correctly output.

In order to solve the above problems, the inventors of the present invention have provided an overheat detection circuit that can accurately detect the temperature of a semiconductor device even at a high temperature and does not output an erroneous detection result.

In order to solve the previous problems, the overheat detecting circuit of the present invention is constructed as follows.

As a first PN junction element as a temperature sensing element, a constant current circuit that supplies a bias current to the first PN junction element, a comparator that compares a voltage generated by the first PN junction element with a reference voltage, and a reference to a high temperature The second PN junction element in which the voltage circuit flows a leakage current and the third PN junction element in which the leakage current of the constant current circuit is bypassed at a high temperature.

According to the overheat detecting circuit of the present invention, the temperature of the semiconductor device can be accurately detected even at a high temperature, and a correct detection result can be output.

10‧‧‧ reference voltage section

11‧‧‧ reference voltage circuit

12‧‧‧Second PN junction element

20‧‧‧Temperature sensing department

21‧‧‧First PN junction element

22‧‧‧Constant current circuit

23‧‧‧ Third PN junction element

30‧‧‧ Comparator

31‧‧‧ PMOS transistor

32‧‧‧ PMOS transistor

33‧‧‧NMOS transistor

34‧‧‧NMOS transistor

35‧‧‧Constant current circuit

36‧‧‧Constant current circuit

37‧‧‧NMOS transistor

38‧‧‧Four PN junction element

OUT‧‧‧ output terminal

Fig. 1 is a circuit diagram of a superheat detecting circuit of the present embodiment.

Fig. 2 is a circuit diagram of a comparator of the overheat detecting circuit of the embodiment.

[Fig. 3] A circuit diagram of a prior overheat detecting circuit.

Hereinafter, the present embodiment will be described with reference to the drawings. Bright.

Fig. 1 is a circuit diagram of a superheat detecting circuit of this embodiment.

The overheat detecting circuit of the present embodiment includes a reference voltage unit 10, a temperature sensing unit 20, and a comparator 30. The reference voltage unit 10 includes a reference voltage circuit 11 and a second PN junction element 12. The temperature sensing unit 20 includes a first PN junction element 21, a constant current circuit 22, and a third PN junction element 23. The first PN junction element 21 serves as a temperature sensing element. The second PN junction element 12 and the third PN junction element 23 are elements for adjusting leakage current at high temperatures.

The second PN junction element 12 and the reference voltage circuit 11 are connected in series between the power supply terminal and the ground terminal, and the reference voltage Vref is outputted from the connection point. The constant current circuit 22 and the first PN junction element 21 are connected in series between the power supply terminal and the ground terminal, and the voltage Vpn corresponding to the temperature is output from the connection point. The first PN junction element 21 is biased at a constant current of the constant current circuit 22. The third PN junction element 23 is connected between its connection point and the ground terminal.

Fig. 2 is a circuit diagram of a comparator 30 of the overheat detecting circuit of the embodiment.

The comparator 30 includes PMOS transistors 31 and 32, NMOS transistors 33, 34, and 37, constant current circuits 35 and 36, and a fourth PN junction element 38. The PMOS transistors 31, 32 and the NMOS transistors 33, 34 and the constant current circuit 35 constitute an initial stage amplifier. The NMOS transistor 37 and the constant current circuit 36 constitute an amplifier of the second stage. The fourth PN junction element 38 is circulated with leakage current at a high temperature to pull down the comparator 30 The components of the output terminals.

The initial stage amplifier differential input is connected to the input terminal of the comparator, and the output terminal is connected to the gate of the NMOS transistor 37. The constant current circuit 36 and the NMOS transistor 37 are connected in series between the power supply terminal and the ground terminal, and the connection point is connected to the output terminal of the comparator 30. The fourth PN junction element 38 is connected between the connection point of the constant current circuit 36 and the NMOS transistor 37 and the ground terminal.

The comparator 30 inputs the reference voltage Vref and the voltage Vpn, and outputs the comparison result from the output terminal to the output terminal OUT of the overheat detecting circuit.

Next, the operation of the overheat detecting circuit of the present embodiment will be described.

The first PN junction element 21, which is a temperature sensing element, generates a voltage Vpn corresponding to the temperature. The comparator 30 detects the overheated state by comparing the reference voltage Vref output from the reference voltage circuit 11 with the voltage Vpn.

Since the first PN junction element 21 is biased by the constant current of the constant current circuit 22, the voltage Vpn represents a negative temperature characteristic. Therefore, if the ambient temperature becomes high, the voltage Vpn will become low. Then, when the voltage Vpn is lower than the reference voltage Vref, the comparator 30 outputs a signal L indicating the overheated state.

The constant current circuit 22 is in a state in which a current mirror circuit including a PMOS transistor is provided. When the temperature is high, a leakage current is generated between the drain terminal of the PMOS transistor and the substrate, and the current is increased. and so, Since the bias current of the first PN junction element 21 increases, the voltage Vpn becomes higher than the desired voltage. That is, the overheat detection circuit becomes unable to detect overheating at a predetermined temperature.

Here, the overheat detecting circuit of the present embodiment is connected to the connection point of the constant current circuit 22 and the first PN junction element 21, and the third PN junction element 23 is connected. The third PN junction element 23 is connected such that the leakage current increases when the temperature is high, and the leakage current of the constant current circuit 22 flows to the ground terminal. Therefore, when the temperature is high, since the bias current of the first PN junction element 21 can be prevented from increasing, the voltage Vpn can be a desired voltage. That is, the overheat detection circuit can detect overheating at a predetermined temperature.

Further, since the leakage current between the drain terminal of the saturated NMOS transistor of the reference voltage circuit 11 and the substrate increases, the reference voltage Vref becomes lower than the desired voltage. That is, the overheat detection circuit becomes unable to detect overheating at a predetermined temperature.

Here, the overheat detecting circuit of the present embodiment is connected to the second PN junction element 12 between the power supply terminal and the reference voltage circuit 11. The second PN junction element 12 is connected such that the leakage current increases when the temperature is high, and the leakage current flows through the reference voltage circuit 11.

For example, the reference voltage Vref is generated by the saturation connection of the NMOS transistor with a certain current bias, because the leakage current of the second PN junction element 12 flows into the NMOS transistor that is connected in saturation, so the reference voltage Vref It becomes the desired voltage at high temperatures. That is, the overheat detection circuit can detect overheating at a predetermined temperature.

Further, the leakage current of the transistor constituting the comparator 30 increases, and the internal operation is abnormal, and the temperature cannot be accurately detected and the result cannot be output correctly.

Here, the overheat detecting circuit of the present embodiment is connected to the fourth PN junction element 38 between the output terminal of the comparator 30 and the ground terminal. The fourth PN junction element 38 is designed such that the leakage current increases as the temperature becomes high, and the current of the constant current circuit 36 becomes larger.

For example, when the leakage current of the fourth PN junction element 38 becomes more than the current of the constant current circuit 36 in the vicinity of the temperature at which the overheat detection should be performed, the output terminal of the comparator 30 is output regardless of the ONOFF of the NMOS transistor 37. Signal L. That is, the overheat detection circuit can output a signal detecting overheating in the vicinity of the temperature at which overheat detection should be performed. With this design, the overheat detection circuit does not output an erroneous detection result.

As described above, the overheat detecting circuit of the present embodiment can accurately detect the temperature of the semiconductor device even at a high temperature, and does not output an erroneous detection result.

Claims (3)

An overheat detecting circuit comprising: a first PN junction element as a temperature sensing element; a constant current circuit for supplying a bias current to the first PN junction element; a reference voltage circuit for outputting a reference voltage; and a comparator, Comparing a voltage generated by the first PN junction element with the reference voltage; and characterized in that: the second PN junction element is configured to flow a leakage current to the reference voltage circuit at a high temperature; and the third PN junction element is at a high temperature The leakage current of the constant current circuit is bypassed, and the comparator is provided with a fourth PN element that flows a leakage current at a high temperature. The overheat detection circuit according to claim 1, wherein the comparator includes a differential amplifier circuit that inputs a voltage generated by the PN junction element and the reference voltage, and a MOS transistor that is differentially amplified. The output of the circuit is input to the gate; and the second constant current circuit is connected to the drain of the MOS transistor; The fourth PN junction element is connected to the second constant current circuit; a connection point between the MOS transistor and the second constant current circuit is an output terminal of the comparator. A semiconductor device characterized by comprising the overheat detecting circuit described in claim 1 or 2.